Microwave ablation (MWA) is a form of thermal ablation used in interventional radiology to treat cancer. MWA uses electromagnetic waves in the microwave energy spectrum (300 megahertz to 300 gigahertz) to produce tissue-heating effects. MWA is generally used for minimally invasive treatment and/or palliation of solid tumors in patients. MWA offers several advantages over other ablation technologies such as radiofrequency (RF) and cryoablation including higher temperatures than RF, larger ablation zone volumes, shorter ablation times, and better ablation performance near arteries, which act as heat sinks.
Typically, interstitial antennas used for MWA are implemented using coaxial cables. When a balanced antenna is fed by an unbalanced transmission line unwanted electric currents are excited on the outer conductors of the feeding coaxial cables. If not properly suppressed, these currents can result in undesired heating and potentially ablation of healthy tissue along the insertion path of the antenna. Balanced to unbalanced transformers (Baluns) are generally implemented to solve this problem. A balun uses a hollow circular conductor to encompass the feeding coaxial cable and, depending on the design, may or may not be electrically connected to it.